1. Field of the Invention
The present invention relates to a controller for work implement of construction machinery, a method for controlling a construction machinery, and a program allowing a computer to execute this method.
2. Description of Related Art
For instance, a construction machine such as a hydraulic shovel carries out various types of works by driving a work implement consisting of an arm or a boom, there is the problem that vibrations occur in the work implement when an operation of the work implement is stopped or the work implement is started from the rest state.
In a case where the work implement is driven by an actuator including a hydraulic cylinder, this phenomenon occurs when supply of a hydraulic oil to the actuator is transitionally stopped or supply of a hydraulic oil is started suddenly all at once, and also because an inertial force of the operation machine in the rest state or in the operating state can not smoothly be absorbed.
When vibrations occur in a work implement with large inertia such as a boom or an arm, the entire hydraulic shovel largely swing, so that also an operator operating an operation lever thereof swing with the operability spoiled.
Further, when the work implement is swinging, it is impossible to shift an operation of the work implement to the next one, so that the operation is delayed with the work efficiency lowered. It is possible to suppress vibrations of the work implement in the rest state or upon start of the operations thereof by making the work implement run slowly, but in this state, the performance of the hydraulic shovel is not fully achieved, and the work efficiency is low also in this state.
To overcome the problems as described above, there have been proposed various types of controllers and control methods for suppressing vibration of a work implement (Refer to, for instance, cited reference 1: Japanese Utility Model Publication No. HEI 248602, cited reference 2: Japanese Patent Laid-Open Publication No. HEI 4-181003, cited reference 3: Japanese Patent Laid-Open Publication No. HEI 4-353130, cited reference 4: Japanese Patent Laid-Open Publication No. HEI 9-324443, cited reference 5: Japanese Patent Laid-Open Publication No. HEI 6-222817).
The cited reference 1 discloses that by providing a throttle in a pilot passage, which operates the flow controlling valve, the pilot pressure of a pilot valve, which operates in the interlocking relationship with the operation lever, is throttled, and thereby the flow controlling valve is slowly operated so that the vibration is suppressed.
The technology disclosed in the cited reference 2 is based on the modulation system in which, when an operation of a work implement is stopped by operating a lever thereof, based on the position and speed of the hydraulic cylinder when the deceleration operation starts, a flow rate of a hydraulic oil to the hydraulic cylinder is restricted by dulling an instruction signal to a flow rate control valve, and vibrations are suppressed by selecting the soft mode in which an instruction signal is dulled.
In the technology disclosed in the cited reference 3, in addition to a first flow rate control valve operating according to an instruction signal from a operation lever when feeding a hydraulic oil to a hydraulic cylinder, there is provided a second flow rate control valve which is auxiliary and operates according to a signal from a controller, and when an operation of the work implement is stopped by supplying a hydraulic oil from the first flow rate control valve, also a hydraulic oil is fed at a prespecified rate from the second flow rate control valve to suppress generation of vibrations.
With the technology disclosed in the cited reference 4, when an operation of a work implement is stopped by operating a lever of the work implement, a flow rate of a hydraulic oil fed to the hydraulic cylinder is gradually reduced from that at a starting point of the operation of the operation lever to suppress vibrations of the work implement.
The technology disclosed in the cited reference 5 relates to a welding robot not having any direct connection with construction machinery. Namely, when weaving welding is performed with a welding robot, the phenomenon occurs that the actual amplitude is different from that instructed for weaving due to the resonance characteristics as well as the phase characteristics of the robot, and to solve this problem, reverse transfer functions are applied as filters for compensating the characteristics respectively, and by outputting an instruction for an amplitude through the filters to a driving section to realize weaving welding with the instructed amplitude. It is conceivable to apply this technology for suppressing vibrations in a construction machine.
In the technology disclosed in the cited reference 1, however, even if it is tried to stop operations of a work implement, for instance, by returning a lever of the work implement to the neutral position, the pilot pressure is throttled due to throttling, so that the flow rate control valve operates only slowly.
Because of this feature, the speed change in the work implement is rather slow, so that vibrations are suppressed to some extent, but a long period of time is required until the operation of the work implement is completely stopped, which disadvantageously causes a delay in stopping the machine's operation.
With the technology disclosed in the cited reference 2, a stroke position and the speed are detected immediately after a lever of a work implement is operated and at the same time a stroke position required for smoothly and quickly stopping the machine's operation without causing vibrations is computed according to a result of detection above, and a flow rate of the hydraulic oil is controlled for the stroke position for stopping operations of the work implement, so that a delay in stopping the machine's operation occurs also in this case.
In the technology disclosed in the cited reference 3, an auxiliary electromagnetic valve is required, and the configuration is complicated. In addition, it is necessary to take into considerations a speed of and a load to the work implement for deciding a flow rate from the second flow rate control valve, and therefore it is necessary to previously prepare a plurality of flow rate decision patterns, and also the processing for pattern selection is disadvantageously complicated.
Further in the cited reference 3, only vibrations generated at a point of time when the hydraulic cylinder is topped can be suppressed, and those generated when an operation of the work implement is started can not be suppressed.
With the technology disclosed in the cited reference 4, a flow rate of a hydraulic oil is gradually reduced by dulling a lever operation signal from a lever of a work implement, the flow control valve operate rather slowly like in the case described above.
Therefore, the operation of the work implement is stopped at a point of time in a certain period of time when the machine's lever is operation when a flow rate of the hydraulic oil comes down to zero, which also leads to a result of a delay in stopping operations of the work implement.
With the cited reference 5 disclosing the technology for weaving welding with the welding robot, an instruction signal for an amplitude inputted into the controller is limited to that having a sinusoidal wave, and therefore in construction machines in which a waveform of an input instruction signal substantially varies according to a way of operation of a lever of each work implement, when the technology is applied as it is, it is difficult to completely suppress vibrations.